1. Field of the Invention
The present invention relates to a method and a system for measuring in-situ the acoustic attenuation provided by a hearing protection device worn by a user.
2. Description of Related Art
U.S. Pat. No. 6,687,377 B2 relates to a method for measuring the acoustic attenuation provided by a customized earplug, wherein the earplug is provided with a sound bore extending from the outer side of the earplug to the inner end of the earplug, wherein a remote device is inserted into the outer end of the sound bore, which remote device comprises a first microphone oriented towards the sound bore and a second microphone oriented towards ambience, and wherein test sound is provided by an external loudspeaker. Both the loudspeaker and the remote device are connected to a computer unit on which a measurement program is run. The acoustic attenuation provided by the earplug is calculated from the sound level difference between the first microphone and the second microphone.
U.S. Pat. No. 5,577,511 relates to a method for measuring in-situ the acoustic attenuation provided by an earplug, wherein a probe tube extends through the earplug into the ear canal and wherein the outer end of the probe tube is connected to a first microphone, while a second microphone is provided at the ear for measuring sound pressure levels exterior to the ear canal as a reference microphone. The acoustic attenuation provided by the earplug is calculated from the difference of the sound levels measured by the first and the second microphone. The test sound for the measurement is the user's voice.
U.S. Pat. No. 6,567,524 B1 relates to a customized earplug which comprises an inner microphone oriented towards the ear canal, an outer microphone oriented towards ambience and a loudspeaker oriented towards the ear canal. The earplug may be used for online control and verification of the acoustic attenuation provided by the earplug by generating a test sound by the loudspeaker and analyzing the signal picked up by the inner microphone.
DE 101 17 705 A1 relates to a hearing protection headphone which comprises a microphone oriented towards ambience and into which a hearing protection earplug is integrated which comprises a loudspeaker oriented towards the ear canal and a microphone oriented towards the ear canal for picking up sound in the ear canal for active noise reduction purposes. The microphone of the headphone is used for selectively providing ambient sound to the ear canal via the loudspeaker of the earplug for communication purposes.
It is an object of the invention to provide for a reliable and reproducible method for measuring in-situ the acoustic attenuation provided by a hearing protection device. It is a further object to provide for a corresponding system.